ISO 14705

• Abstract:

  This document specifies a test method for determining the Vickers and Knoop hardness of monolithic fine ceramics at room temperature.

• Status: Not Published
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: ISO/TC 206 - Fine ceramics
• Drafting Committee: ISO/TC 206 - Fine ceramics
• Current Stage: 6000 - International Standard under publication
• Start Date: 06-Aug-2026
• Completion Date: 19-Sep-2026

• Consolidates: prEN ISO 14705 - Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for hardness of monolithic ceramics at room temperature (ISO/DIS 14705:2025)
• Effective Date: 12-Feb-2026
• Revises: ISO 14705:2016 - Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for hardness of monolithic ceramics at room temperature
• Effective Date: 08-Oct-2022

Overview

ISO 14705:2016 is an international standard developed by ISO (International Organization for Standardization) specifically for the testing of hardness in monolithic fine ceramics (advanced ceramics and advanced technical ceramics) at room temperature. This standard details the procedures for determining both Vickers and Knoop hardness values, providing a clear, repeatable methodology suitable for industry and research purposes. By standardizing hardness testing methods, ISO 14705 ensures consistent, reliable results across laboratories and supports quality assurance in the production and application of advanced ceramic materials.

Key Topics

• Scope of the Standard:
  ISO 14705 applies to monolithic fine ceramics and advanced technical ceramics, specifying hardness testing at room temperature (typically 10°C to 35°C).

• Test Methods Covered:

  • Vickers Hardness Test: Uses a diamond pyramid indenter to measure hardness based on the size of the resulting impression.
  • Knoop Hardness Test: Employs an elongated diamond indenter, better suited for brittle or thin samples.

• Testing Requirements:

  • Preparation of the ceramic sample surface to ensure accuracy.
  • Utilization of calibrated testing machines and indenters according to referenced ISO standards.
  • Specific details for valid indentation, measurement, and spacing to minimize errors and ensure data integrity.
  • Reporting requirements that ensure traceability and repeatability of results.

• Significance of Hardness Testing:
  Hardness is a critical material property for ceramics, impacting wear resistance, mechanical strength, and reliability in demanding applications.

Applications

ISO 14705 is widely adopted by:

• Manufacturers and Quality Control:
  Used in ceramic material production to control and verify the hardness consistency of batches, ensuring compliance with specifications and anticipated in-service performance.

• Research and Development:
  Supports materials scientists and engineers in developing new advanced ceramics, allowing them to benchmark and compare new formulations or processing methods.

• Component Certification:
  Ensures that ceramic parts-such as cutting tools, biomedical implants, electronic substrates, and wear-resistant components-meet required performance standards for global trade and regulatory compliance.

• Testing Laboratories:
  Provides accredited laboratories with standardized methods for reporting hardness, supporting inter-laboratory compatibility and reliable data sharing.

Related Standards

For a comprehensive ceramic hardness testing and verification program, ISO 14705 should be used in conjunction with the following standards:

• ISO 6507-1: Metallic materials - Vickers hardness test - Part 1: Test method
• ISO 6507-2: Metallic materials - Vickers hardness test - Part 2: Verification and calibration of testing machines
• ISO 4545-1: Metallic materials - Knoop hardness test - Part 1: Test method
• ISO 4545-2: Metallic materials - Knoop hardness test - Part 2: Verification and calibration of testing machines

These related ISO standards provide additional detail and support for indenter calibration, machine verification, and hardness measurement for both metallics and ceramics.

Benefits and Practical Value

• Enhanced Reliability:
  Adopting ISO 14705 ensures that hardness measurements are accurate, comparable, and repeatable between different operators and laboratories.

• Global Acceptance:
  Using internationally recognized hardness testing methods facilitates certification, trade, and regulatory approval for advanced ceramic products.

• Quality Assurance:
  Reduces the risk of material failure in service, as components can be validated against universally accepted hardness metrics.

• R&D Support:
  Enables benchmarking and performance optimization for advanced ceramics, accelerating innovation and application development in industries such as aerospace, electronics, and medical devices.

By following ISO 14705, organizations ensure the consistent evaluation of fine ceramics and advanced technical ceramics, promoting material integrity and supporting the continued growth of advanced material technologies.

International
Standard
Fourth edition
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Test method for hardness of
monolithic ceramics at room
temperature
Céramiques techniques — Méthodes d’essai de dureté des
céramiques monolithiques à température ambiante
PROOF/ÉPREUVE
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
PROOF/ÉPREUVE
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Vickers hardness . 2
4.1 Principle .2
4.2 Symbols, abbreviated terms and designations .2
4.3 Significance and use .4
4.4 Apparatus .4
4.5 Test pieces .5
4.6 Procedure .5
4.7 Accuracy and uncertainties .8
4.8 Test report .8
5 Knoop hardness .12
5.1 Principle . 12
5.2 Symbols and designations . 12
5.3 Significance and use .14
5.4 Apparatus .14
5.5 Test pieces . . 15
5.6 Procedure . 15
5.7 Accuracy and uncertainty .16
5.8 Test report .17
Bibliography .21
PROOF/ÉPREUVE
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics, in collaboration with
the European Committee for Standardization (CEN) Technical Committee CEN/TC 184, Advanced technical
ceramics, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna
Agreement).
This fourth edition cancels and replaces the third edition (ISO 14705:2016), which has been technically
revised.
The main changes are as follows:
— clarification of the required resolution of the diagonal measuring system (4.4.3 and 5.4.3);
— modification of the required measurement accuracy (clauses 4.6.12 and 5.6.12).
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
PROOF/ÉPREUVE
iv
International Standard ISO 14705:2026(en)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test method for hardness of monolithic ceramics
at room temperature
1 Scope
This document specifies a test method for determining the Vickers and Knoop hardness of monolithic fine
ceramics at room temperature.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 4545-1, Metallic materials — Knoop hardness test — Part 1: Test method
ISO 4545-2, Metallic materials — Knoop hardness test — Part 2: Verification and calibration of testing machines
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 6507-2, Metallic materials — Vickers hardness test — Part 2: Verification and calibration of testing machines
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
Vickers hardness
value obtained by dividing the applied force by the projected area of the indentation, calculated from the
arithmetic mean of the measured diagonals of the indentations, assuming that the indentation is a permanent
imprint of the undeformed indenter
Note 1 to entry: Vickers hardness may be expressed either
a) with units of GPa, obtained by dividing the applied force in N by the projected area of the indentation in mm ,
or
b) as a dimensionless Vickers hardness number, obtained by dividing the applied force in N by a scaling
factor corresponding to the standard gravity (9,806 65 m/s ) and by the projected area of the
indentation in mm .
Note 2 to entry: The scaling factor ensures that the resulting dimensionless value is numerically identical to legacy
calculations historically expressed in kgf/mm .
PROOF/ÉPREUVE
3.2
Vickers indenter
indenter in the shape of a right-angle pyramid with a square base and an angle between opposite faces of
136°
Note 1 to entry: See Table 1 and Figure 1.
3.3
Knoop hardness
value obtained by dividing the applied force by the projected area of the indentation, calculated from the
measured long diagonal of the indentation, assuming that the indentation is a permanent imprint of the
undeformed indenter
Note 1 to entry: The Knoop hardness may be expressed either
a) with units of GPa, obtained by dividing the applied force in N by the projected area of the indentation in mm ,
or
b) as a dimensionless Knoop hardness number, obtained by dividing the applied force in N by a scaling
factor corresponding to the standard gravity (9,806 65 m/s ) and by the projected area of the
indentation in mm .
Note 2 to entry: The scaling factor ensures that the resulting dimensionless value is numerically identical to legacy
calculations historically expressed in kgf/mm .
3.4
Knoop indenter
indenter in the shape of a rhombic-based pyramid with the two angles between the opposite edges at 172,5°
and 130°
Note 1 to entry: See Table 3 and Figure 6.
4 Vickers hardness
4.1 Principle
Forcing a diamond indenter in the form of a right-angle pyramid with a square base, and with a specified
angle between opposite faces at the vertex into the surface of a test piece and measuring the length of the
diagonals of the indentation left in the surface after removal of the test force, F. See Figure 1 and Figure 2.
4.2 Symbols, abbreviated terms and designations
4.2.1 See Table 1, Figure 1 and Figure 2.
4.2.2 The Vickers hardness is expressed either as a physical unit of pressure (GPa) or as a conventional,
dimensionless hardness number.
When using SI unit (GPa), the hardness value is denoted by the unit symbol GPa, followed by the designation
HV and a value representing the exact test force in Newtons (N)
EXAMPLE 1 15,0 GPa HV 9,807 N represents a Vickers hardness of 15,0 GPa, determined with a test force of 9,807 N.
When using the dimensionless Vickers hardness number, the value is denoted by the symbol HV, preceded by the
hardness value and followed by a force indicator number representing the nominal test force (see Table 2).
EXAMPLE 2 1 500 HV 1 represents a Vickers hardness number of 1 500, determined with a test force indicator of 1
(corresponding to a nominal test force of 9,807 N).
PROOF/ÉPREUVE
Table 1 — Symbols, abbreviated terms and designations for Vickers hardness testing
Symbol or
abbreviated Designation
term
α Angle between the opposite faces at the vertex of the pyramidal indenter (136° ± 0,5°)
F Test force, in newtons
d Arithmetic mean, in millimetres, of the two diagonals, d and d
1 2
HV Vickers hardness
Test force
Constant
Surfaceareaofindentation
a) Units of GPa
136
2F sin
F
 0,001  0,001854
d d
b) Hardness number (no units specified)

136 136
2F sin 2F sin
1 F
2 2
   0,10197  0,1891
22 2
g
d d d
c Arithmetic mean of the half of the two median crack lengths, 2c and 2c
1 2
SD Standard deviation
HV HV

n

n 1
where
HV

n
HV is the arithmetic mean of the Vickers hardness  ;
n
HV is the HV obtained from nth indentation;
n
n is the number of indentations.
NOTE The scaling constant 0,10197 , where g is the acceleration of gravity is a historical mathematical
g 9,80665
wrapper ensuring that the resulting hardness number remains numerically identical to legacy engineering records previously
calculated in kgf/mm .
Table 2 — Hardness symbols and the nominal values of test forces, F, for Vickers hardness testing
Test force, F
Hardness symbol
(nominal value)
HV 0,5 4,903 N
HV 1 9,807 N
HV 2 19,61 N
HV 3 29,42 N
HV 5 49,03 N
HV 10 98,07 N
HV 20 196,1 N
PROOF/ÉPREUVE
==
Figure 1 — Vickers indenter (diamond pyramid)
Figure 2 — Vickers indentation
4.3 Significance and use
Vickers indentation diagonal lengths are approximately 2,8 times shorter than the long diagonal of Knoop
indentations, and the indentation depth is approximately 1,5 times deeper than Knoop indentations made
at the same force. Vickers indentations are influenced less by the specimen surface flatness, parallelism of
the diamond axis to the test piece surface normal, and surface finish than Knoop indentations, but these
parameters should be considered, nonetheless. Vickers indentations are much more likely to cause cracks in
fine ceramics than Knoop indentations. Conversion between hardness scales shall not be made.
Vickers indentations on metallic materials are mainly formed by the plastic deformation. However, Vickers
indentations on fine ceramics are formed by micro-cracking and micro-fracture, besides plastic deformation.
This difference shall be noted for comparing the hardness of metals and ceramics.
4.4 Apparatus
4.4.1 Testing machine, capable of applying a predetermined test force in the range of 4,903 N to 98,07 N,
preferably 9,807 N, in accordance with ISO 6507-2. Verification of the test force shall be carried out in
accordance with ISO 6507-2.
PROOF/ÉPREUVE
4.4.2 Diamond indenter, in the shape of a right-angle pyramid with a square base, in accordance with
ISO 6507-1 and ISO 6507-2. Verification of the indenter shall be carried out in accordance with ISO 6507-2.
4.4.3 Diagonal measuring system. Magnifications should be provided so that the diagonal can be
enlarged to greater than 25 % but less than 75 % of the maximum possible optical field of view as many
objective lenses are nonlinear towards the edge of the field of view.
The resolution required of the diagonal measuring system depends on the size of the smallest indentation
to be measured and shall be in accordance with Table 3. In determining the resolution of the measuring
system, the resolution of the microscope optics, the digital resolution of the measuring scale and the step-
size of any stage movement, where applicable, should be taken into account.
Table 3 — Resolution of the measuring system
Diagonal length, d
Resolution of the measuring sys-
Maximum permissible error
tem
mm
d < 0,050 0,000 25 mm 0,000 5 mm
0,050 ≤ d 0,5 % of d 1 % of d
A numerical aperture (NA) between 0,60 and 0,95 for the objective lens for the microscope is recommended.
NOTE 1 The apparent length of a Vickers indentation increases as the resolving power and NA of a lens increases.
The range of NA specified by this test method corresponds to 40 to 100× objective lenses. The higher power lenses can
have higher resolution, but the contrast between the indentation tips and the polished surface can be lower.
Verification of the measuring device shall be carried out in accordance with ISO 6507-2.
NOTE 2 Indirect verification can be carried out by means of standardized blocks calibrated in accordance with
ISO 6507-3, following ISO 6507-2, or other approved and traceable ceramic standard reference blocks.
4.5 Test pieces
4.5.1 The test shall be carried out on a surface which is smooth, flat and free from foreign matter. The
test piece shall be polished to permit accurate measurement of the diagonal lengths of the indentation.
Preparation shall be carried out in such a way that any alteration of the surface hardness is minimized.
Surfaces shall not be thermally or chemically etched. If applicable, residual surface stresses shall be removed
by suitable polishing or annealing procedures.
4.5.2 The thickness of the test piece shall be at least 1,5 times the diagonal of the indentation, d, at least
2 times the crack length, c, and at least 0,5 mm, whichever is greater. No indentation damage shall be visible
at the back of the test piece upon completion of the test.
4.6 Procedure
4.6.1 In general, the test shall be carried out at room temperature within the limits of 10 °C to 35 °C. Tests
carried out under controlled conditions shall be made at a temperature of 23 °C ± 5 °C.
4.6.2 The test force shall be 9,807 N. In cases where significant chipping or lateral crack-spalling occurs
or where the impression is too faint, the test forces within the range 4,903 N to 196,1 N, listed in Table 2,
may be used. Other instances where a heavier load may be required are where the grain structure is very
coarse and the indentation area at lower loads can contact only a few grains of the material (e.g. a multiphase
material).
4.6.3 The following items shall be confirmed before the test.
a) Check the zero of the measuring system.
PROOF/ÉPREUVE
b) Check the measuring system using a calibrated scale or certified indentation in a test block.
c) Check the operation of the loading system by performing a test on a certified test block.
d) Check the condition of the indenter by examining the indentation made in the test block. Replace the
indenter, if necessary, by taking into account the conditions given in 4.6.10.
e) A test block with high hardness has to be used in order to obtain impressions in the same size range as
expected during tests on ceramics.
4.6.4 The indenter shall be cleaned prior to and during the test series, as ceramic powders or fragments
from the ceramic test piece can adhere to the diamond indenter.
4.6.5 The test piece shall be placed on a rigid support. The support surface shall be clean and free from
foreign matter. The test piece shall lie firmly on the support, so that displacement cannot occur during the
test.
4.6.6 Carefully adjust the illumination and focusing conditions, in order to obtain the optimum view and
clarity of the indentation. Both indentation tips shall be in focus at the same time. Do not change the focus
when measuring the distance from tip to tip.
4.6.7 Bring the indenter into contact with the test surface and apply the test force in a direction
perpendicular to the surface, without shock or vibration, until the applied force attains the specified value.
The time from the initial application of the force until the full test force is reached shall not be less than 1 s
nor greater than 5 s. The duration of application of the constant maximum test force shall be 15 s.
4.6.8 Throughout the test, the apparatus shall be protected from shock or vibration.
4.6.9 The distance between the centre of any indentations and the edge of the test piece shall be at least
2,5 times the mean diagonal of the indentation, and at least 5 times the mean length of the crack, as shown
in Figure 3. The distance between the centres of two adjacent indentations shall be at least 4 times the mean
diagonal of the indentation, and at least 5 times the mean length of the crack, as shown in Figure 3. If two
adjacent indentations differ in size and crack length, the spacing shall be based on the mean diagonal of the
larger indentation and the longer crack length.

PROOF/ÉPREUVE
Key
1 edge of test piece
2 indentations
c length from the centre of indentation to the end of crack
d length of indent diagonal
l distance between centres of indentations
l ≥ 4d and 5c
l distance from centre of indentation to the edge of sample
l ≥ 2,5d and 5c
Figure 3 — Closest permitted spacing between indentations and from indentation to the test piece
edge for Vickers indentations
4.6.10 The satisfactory condition of the indenter shall be verified frequently. Any irregularities in the shape
of the indentation can indicate chipping, cracking or other deterioration of the indenter. If the examination
of the indenter confirms this, then the test shall be rejected, and the indenter replaced.
4.6.11 If there is excessive cracking from the indentation tips and sides, then the indentation shall be
rejected and go unmeasured. If one of the tips of an indentation falls into a pore, the indentation shall be
rejected. If the indentation lies in or on a large pore, the indentation shall be rejected. Figure 4 provides
guidance on this assessment.
4.6.12 Measure the length of the two diagonals following the required resolution given in Table 3. The
arithmetical mean of two readings shall be taken for the calculation of the Vickers hardness. If the difference
of the two diagonals is more than 5 % of the mean value (see Figure 4), the result shall be rejected, and
a check made of the parallelism and flatness of the test piece, and of the alignment of the indenter. The
manufacturer's instructions on the proper usage of the measuring crosshairs shall be followed. Figure 5 is
provided for guidance. The use of optical methods to enhance contrast (like Nomarski interferences) is not
permitted.
4.6.13 At least five valid indentations shall be made for obtaining a mean result in accordance with this
document.
4.6.14 Calculate the Vickers hardness, HV, for each valid indentation, using the formula in Table 1. Calculate
the mean hardness for all valid indentations and the standard deviation. The calculated Vickers hardnes
...

ISO/FDISPRF 14705:2026(en)
ISO/TC 206/WG 7
Secretariat: JISC
Date: 2026-05-2907-07
Fine ceramics (advanced ceramics, advanced technical ceramics) —
Test method for hardness of monolithic ceramics at room
temperature
Céramiques techniques — Méthodes d’essai de dureté des céramiques monolithiques à température ambiante
PROOF
ThiThis drs drafaft is t is submitted tsubmitted too a a p parallel arallel vovote in ISOte in ISO, CE, CEN.N.

ISO #####-#:####(X/PRF 14705:2026(en)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: [e-mail]
Website: www.iso.orgwww.iso.org
Published in Switzerland
ii © ISO #### 2026 – All rights reserved
ii
ISO/DISPRF 14705:20252026(en)
Contents
Foreword . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Vickers hardness . 2
4.1 Principle . 2
4.2 Symbols, abbreviated terms and designations . 2
4.3 Significance and use . 5
4.4 Apparatus . 5
4.5 Test pieces . 6
4.6 Procedure . 6
4.7 Accuracy and uncertainties . 9
4.8 Test report . 10
5 Knoop hardness . 15
5.1 Principle . 15
5.2 Symbols and designations . 15
5.3 Significance and use . 18
5.4 Apparatus . 18
5.5 Test pieces . 19
5.6 Procedure . 19
5.7 Accuracy and uncertainty . 20
5.8 Test report . 20
Bibliography . 27

Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Vickers hardness . 2
4.1 Principle . 2
4.2 Symbols, abbreviated terms and designations . 2
4.3 Significance and use . 5
4.4 Apparatus . 5
4.5 Test pieces . 5
4.6 Procedure . 6
4.7 Accuracy and uncertainties . 8
4.8 Test report . 9
5 Knoop hardness . 12
5.1 Principle . 12
5.2 Symbols and designations . 12
iii
ISO #####-#:####(X/PRF 14705:2026(en)
5.3 Significance and use . 14
5.4 Apparatus . 15
5.5 Test pieces . 15
5.6 Procedure . 16
5.7 Accuracy and uncertainty . 17
5.8 Test report . 17
Bibliography . 21
iv © ISO #### 2026 – All rights reserved
iv
ISO/DISPRF 14705:20252026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics, in collaboration with the
European Committee for Standardization (CEN) Technical Committee CEN/TC 184, Advanced technical
ceramics, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna
Agreement).
This fourth edition cancels and replaces the third edition (ISO 14705:2016), which has been technically
revised.
The main changes are as follows:
— — clarification of the required resolution of the diagonal measuring system (4.4.3(1.1.1 and 5.4.3);5.4.3);
— — modification of the required measurement accuracy (clauses 4.6.12(4.6.12 and 5.6.12).5.6.12).
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.htmlwww.iso.org/members.html.

v
DRAFT International Standard ISO/DIS 14705:2025(en)

Fine ceramics (advanced ceramics, advanced technical ceramics) —
Test method for hardness of monolithic ceramics at room
temperature
1 Scope
This document specifies a test method for determining the Vickers and Knoop hardness of monolithic fine
ceramics at room temperature.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 4545--1, Metallic materials — Knoop hardness test — Part 1: Test method
ISO 4545--2, Metallic materials — Knoop hardness test — Part 2: Verification and calibration of testing
machines
ISO 6507--1, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 6507--2, Metallic materials — Vickers hardness test — Part 2: Verification and calibration of testing
machines
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
3.1 3.1
Vickers hardness
value obtained by dividing the applied force by the projected area of the indentation, calculated from the
arithmetic mean of the measured diagonals of the indentations, assuming that the indentation is a permanent
imprint of the undeformed indenter
Note 1 to entry: Vickers hardness may be expressed either
a) with units of GPa, obtained by dividing the applied force in N by the projected area of the indentation in mm ,
or
b) as a dimensionless Vickers hardness number, obtained by dividing the applied force in N by a scaling factor
2 2
corresponding to the standard gravity (9,806 65 m/s²)s ) and by the projected area of the indentation in mm .
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Note 2 to entry: The scaling factor ensures that the resulting dimensionless value is numerically identical to legacy
calculations historically expressed in kgf/mm².mm .
3.2 3.2
Vickers indenter
indenter in the shape of a right-angle pyramid with a square base and an angle between opposite faces of 136°
Note 1 to entry: See Table 1Table 1 and Figure 1.Figure 1 .
3.3 3.3
Knoop hardness
value obtained by dividing the applied force by the projected area of the indentation, calculated from the
measured long diagonal of the indentation, assuming that the indentation is a permanent imprint of the
undeformed indenter
Note 1 to entry: The Knoop hardness may be expressed either
a) with units of GPa, obtained by dividing the applied force in N by the projected area of the indentation in mm ,
or
b) as a dimensionless Knoop hardness number, obtained by dividing the applied force in N by a scaling factor
2 2
corresponding to the standard gravity (9,806 65 m/s²)s ) and by the projected area of the indentation in mm .
Note 2 to entry: The scaling factor ensures that the resulting dimensionless value is numerically identical to legacy
calculations historically expressed in kgf/mm².mm .
3.4 3.4
Knoop indenter
indenter in the shape of a rhombic-based pyramid with the two angles between the opposite edges at 172,5°
and 130°
Note 1 to entry: See Table 3Table 3 and Figure 6.Figure 6 .
4 Vickers hardness
4.1 Principle
Forcing a diamond indenter in the form of a right-angle pyramid with a square base, and with a specified angle
between opposite faces at the vertex into the surface of a test piece and measuring the length of the diagonals
of the indentation left in the surface after removal of the test force, F. See Figure 1 and Figure 2.See Figure 1
and Figure 2 .
4.2 Symbols, abbreviated terms and designations
4.2.1 4.2.1 See Table 1, Figure 1 and Figure 2.
4.2.1 4.2.2 See Table 1 , Figure 1 and Figure 2 .
4.2.2 The Vickers hardness is expressed either as a physical unit of pressure (GPa) or as a conventional,
dimensionless hardness number.
When using SI unit (GPa), the hardness value is denoted by the unit symbol GPa, followed by the designation
HV and a value representing the exact test force in Newtons (N)
EXAMPLE 1 15,0 GPa HV 9,807 N represents a Vickers hardness of 15,0 GPa, determined with a test force of 9,807 N.
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ISO/DISPRF 14705:20252026(en)
When using the dimensionless Vickers hardness number, the value is denoted by the symbol HV, preceded by the
hardness value and followed by a force indicator number representing the nominal test force (see Table 2).Table 2 ).
EXAMPLE 2 1 500 HV 1 represents a Vickers hardness number of 1 500, determined with a test force indicator of 1
(corresponding to a nominal test force of 9,807 N).
Table 1 — Symbols, abbreviated terms and designations for Vickers hardness testing
Symbol or
abbreviated Designation
term
α Angle between the opposite faces at the vertex of the pyramidal indenter (136° ± 0,5°)
F Test force, in newtons
d Arithmetic mean, in millimetres, of the two diagonals, d1 and d2
HV Vickers hardness
Test force
=Constant
Test force
Surface area of indentation
=  Constant  ×
Surface area of indentation
a) Units of GPa
136
2F sin
F
= 0,001 = 0,001 854
136°
2𝐹sin
𝐹
dd
=  0,001    =  0,001854
2 2
𝑑 𝑑
b) Hardness number (no units specified)
136° 136° 136° 136°
2𝐹 𝑠𝑖𝑛   2𝐹sin  2𝐹 𝑠𝑖𝑛   2𝐹sin
1 𝐹
2 2 2 2
= =   =  0,101 97    =      =  0,189 1
2 2 2 2 2
𝑔 𝑑 𝑑 𝑑 𝑑 𝑑
c Arithmetic mean of the half of the two median crack lengths, 2c and 2c
1 2
SD Standard deviation
HV − HV
( )
 n
=
¯
∑(HV − HV )
n − 1
𝑛
√
=
𝑛 − 1
where
HV
HV
 n ∑HV
𝑛
is the arithmetic mean of the Vickers hardness ;=   ;
=
¯
𝑛
HV
n
HV is the HV obtained from nth indentation;
n
n is the number of indentations.
1 1 1
NOTE The scaling constant   =     =    =     =  0,101 97, where g is the acceleration of gravity is a historical
𝑔 9,806 65 9,806 65
mathematical wrapper ensuring that the resulting hardness number remains numerically identical to legacy engineering records
previously calculated in kgf/mm².mm .
Table 2 — Hardness symbols and the nominal values of test forces, F, for Vickers hardness testing
Test force, F
Hardness symbol
(nominal value)
HV 0,5 4,903 N
HV 1 9,807 N
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Test force, F
Hardness symbol
(nominal value)
HV 2 19,61 N
HV 3 29,42 N
HV 5 49,03 N
HV 10 98,07 N
HV 20 196,1 N
Figure 1 — Vickers indenter (diamond pyramid)
4 © ISO #### 2026 – All rights reserved
ISO/DISPRF 14705:20252026(en)
Figure 2 — Vickers indentation
4.3 Significance and use
Vickers indentation diagonal lengths are approximately 2,8 times shorter than the long diagonal of Knoop
indentations, and the indentation depth is approximately 1,5 times deeper than Knoop indentations made at
the same force. Vickers indentations are influenced less by the specimen surface flatness, parallelism of the
diamond axis to the test piece surface normal, and surface finish than Knoop indentations, but these
parameters should be considered, nonetheless. Vickers indentations are much more likely to cause cracks in
fine ceramics than Knoop indentations. Conversion between hardness scales shall not be made.
Vickers indentations on metallic materials are mainly formed by the plastic deformation. However, Vickers
indentations on fine ceramics are formed by micro-cracking and micro-fracture, besides plastic deformation.
This difference shall be noted for comparing the hardness of metals and ceramics.
4.4 Apparatus
4.4.1 4.4.1 Testing machine, capable of applying a predetermined test force in the range of 4,903 N to
98,07 N, preferably 9,807 N, in accordance with ISO 6507--2. Verification of the test force shall be carried out
in accordance with ISO 6507--2.
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4.4.2 4.4.2 Diamond indenter, in the shape of a right-angle pyramid with a square base, in accordance
with ISO 6507--1 and ISO 6507--2. Verification of the indenter shall be carried out in accordance with
ISO 6507--2.
4.4.3 4.4.3 Diagonal measuring system,
4.4.44.4.3 . Magnifications should be provided so that the diagonal can be enlarged to greater than 25 %
but less than 75 % of the maximum possible optical field of view as many objective lenses are nonlinear
towards the edge of the field of view.
The resolution required of the diagonal measuring system depends on the size of the smallest indentation to
be measured and shall be in accordance with Table 3.Table 3 . In determining the resolution of the measuring
system, the resolution of the microscope optics, the digital resolution of the measuring scale and the step-size
of any stage movement, where applicable, should be taken into account.
Table 3 — Resolution of the measuring system
Diagonal length, d
Resolution of the measuring
Maximum permissible error
system
mm
d < 0,050 0,000 25 mm 0,000 5 mm
0,050 ≤ d 0,5 % of d 1 % of d
A numerical aperture (NA) between 0,60 and 0,95 for the objective lens for the microscope is recommended.
NOTE 1 The apparent length of a Vickers indentation increases as the resolving power and NA of a lens increases. The
range of NA specified by this test method corresponds to 40 to 100× objective lenses. The higher power lenses can have
higher resolution, but the contrast between the indentation tips and the polished surface can be lower.
Verification of the measuring device shall be carried out in accordance with ISO 6507--2.
NOTE 2 Indirect verification can be carried out by means of standardized blocks calibrated in accordance with
ISO 6507--3, following ISO 6507--2, or other approved and traceable ceramic standard reference blocks.
4.5 Test pieces
4.5.1 4.5.1 The test shall be carried out on a surface which is smooth, flat and free from foreign matter.
The test piece shall be polished to permit accurate measurement of the diagonal lengths of the indentation.
Preparation shall be carried out in such a way that any alteration of the surface hardness is minimized.
Surfaces shall not be thermally or chemically etched. If applicable, residual surface stresses shall be removed
by suitable polishing or annealing procedures.
4.5.2 4.5.2 The thickness of the test piece shall be at least 1,5 times the diagonal of the indentation, d, at
least 2 times the crack length, c, and at least 0,5 mm, whichever is greater. No indentation damage shall be
visible at the back of the test piece upon completion of the test.
4.6 Procedure
4.6.1 4.6.1 In general, the test shall be carried out at room temperature within the limits of 10 °C to 35 °C.
Tests carried out under controlled conditions shall be made at a temperature of 23 °C ± 5 °C.
4.6.2 4.6.2 The test force shall be 9,807 N. In cases where significant chipping or lateral crack-spalling
occurs or where the impression is too faint, the test forces within the range 4,903 N to 196,1 N, listed in
Table 2,Table 2 , may be used. Other instances where a heavier load may be required are where the grain
structure is very coarse and the indentation area at lower loads can contact only a few grains of the material
(e.g. a multiphase material).
4.6.3 4.6.3 The following items shall be confirmed before the test.
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a) a) Check the zero of the measuring system.
b) b) Check the measuring system using a calibrated scale or certified indentation in a test block.
c) c) Check the operation of the loading system by performing a test on a certified test block.
d) d) Check the condition of the indenter by examining the indentation made in the test block.
Replace the indenter, if necessary, by taking into account the conditions given in 4.6.10.4.6.10.
e) e) A test block with high hardness has to be used in order to obtain impressions in the same size
range as expected during tests on ceramics.
4.6.4 4.6.4 The indenter shall be cleaned prior to and during the test series, as ceramic powders or
fragments from the ceramic test piece can adhere to the diamond indenter.
4.6.5 4.6.5 The test piece shall be placed on a rigid support. The support surface shall be clean and free
from foreign matter. The test piece shall lie firmly on the support, so that displacement cannot occur during
the test.
4.6.6 4.6.6 Carefully adjust the illumination and focusing conditions, in order to obtain the optimum view
and clarity of the indentation. Both indentation tips shall be in focus at the same time. Do not change the focus
when measuring the distance from tip to tip.
4.6.7 4.6.7 Bring the indenter into contact with the test surface and apply the test force in a direction
perpendicular to the surface, without shock or vibration, until the applied force attains the specified value.
The time from the initial application of the force until the full test force is reached shall not be less than 1 s nor
greater than 5 s. The duration of application of the constant maximum test force shall be 15 s.
4.6.8 4.6.8 Throughout the test, the apparatus shall be protected from shock or vibration.
4.6.9 4.6.9 The distance between the centre of any indentations and the edge of the test piece shall be at
least 2,5 times the mean diagonal of the indentation, and at least 5 times the mean length of the crack, as shown
in Figure 3.Figure 3 . The distance between the centres of two adjacent indentations shall be at least 4 times
the mean diagonal of the indentation, and at least 5 times the mean length of the crack, as shown in
Figure 3.Figure 3 . If two adjacent indentations differ in size and crack length, the spacing shall be based on
the mean diagonal of the larger indentation and the longer crack length.

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Key
1 edge of test piece
2 indentations
c length from the centre of indentation to the end of crack
d length of indent diagonal
l1 distance between centres of indentations
l1 ≥ 4d and 5c
l2 distance from centre of indentation to the edge of sample
l2 ≥ 2,5d and 5c
Figure 3 — Closest permitted spacing between indentations and from indentation to the test piece
edge for Vickers indentations
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4.6.10 4.6.10 The satisfactory condition of the indenter shall be verified frequently. Any irregularities in the
shape of the indentation can indicate chipping, cracking or other deterioration of the indenter. If the
examination of the indenter confirms this, then the test shall be rejected, and the indenter replaced.
4.6.11 4.6.11 If there is excessive cracking from the indentation tips and sides, then the indentation shall be
rejected and go unmeasured. If one of the tips of an indentation falls into a pore, the indentation shall be
rejected. If the indentation lies in or on a large pore, the indentation shall be rejected. Figure 4Figure 4
provides guidance on this assessment.
4.6.12 4.6.12 Measure the length of the two diagonals following the required resolution given in
Table 3.Table 3 . The arithmetical mean of two readings shall be taken for the calc
...